I need to find the approximate speeds of the earth's orbit at perhilion and aphelion (this year, for example, if it makes a difference). I have given myself a crash course in astronomy over the course of the last three months and command a fair if somewhat pedantic understanding of the underlying principles. The earth's mean revolutionary velocity is easily found, but i have not found these precise figures and am not much of a math whiz. Can you help me?

The formula for the velocity of an object at some distance r from the Sun is:

v = sqrt[GM*(2/r - 1/a)]

Where G is the universal gravitational constant, M is the mass of the Sun, and a is the planet's semimajor axis.

At perihelion, Earth's distance from the Sun is r=a(1-e) and at aphelion, it's r=a(1+e).

G=6.673*10-11 N m2/kg2

M=1.989*1030 kg

a=1.496*1011 m

e=0.017

So plugging in the numbers, the speed at perihelion is 30,300 m/s and at aphelion it's 29,300 m/s.

Curious Minds Online

We have 3343 guests and one member online

How Many Were Here?

Total page views since 1997

101979954

Who are We?

Ask an Astronomer is run by volunteers in the Astronomy Department at Cornell University. Most of us are graduate students at Cornell, and all of us do this voluntarily, in our own time, fitting it in around our other work. Please take the time to browse our site and first try to use the resources online to find an answer to your question.